Current results of the PERSEE testbench: the cophasing control and the polychromatic null rate

Stabilizing a nulling interferometer at a nanometric level is the key issue to obtain deep null depths. The PERSEE breadboard has been designed to study and optimize the operation of a cophased nulling bench in the most realistic disturbing environment of a space mission. This presentation focuses on the current results of the PERSEE bench. In terms of metrology, we cophased at 0.33 nm rms for the piston and 80 mas rms for the tip/tilt (0.14% of the Airy disk). A Linear Quadratic Gaussian (LQG) control coupled with an unsupervised vibration identification allows us to maintain that level of correction, even with characteristic vibrations of nulling interferometry space missions. These performances, with an accurate design and alignment of the bench, currently lead to a polychromatic unpolarised null depth of 8.9E-6 stabilized at 3E-7 on the [1.65-2.45] \mum spectral band (37% bandwidth).Comment: 17 pages, 10 figures, proceedings of the Optics+Photonics SPIE conference, San Diego, 201

AMBER : a near infrared focal instrument for the VLTI

10 pagesInternational audienceAMBER is the General User near-infrared focal instrument of the Very Large Telescope interferometer. Its specifications are based on three key programs on Young Stellar Objects, Active Galactic Nuclei central regions, masses and spectra of hot Extra Solar Planets. It has an imaging capacity because it combines up to three beams and very high accuracy measurement are expected from the spatial filtering of beams by single mode fibers and the comparison of measurements made simultaneously in different spectral channels

Alignement et cophasage en temps-réel de systèmes multi-pupilles avec des détecteurs en plan focal sur un object non résolu

International audienceThe alignment of the subapertures is a major challenge for future segmented telescopes and telescope arrays. We show here that a focal plane wave-front sensor using only two images can fully and efficiently align a multiple aperture system, both for the alignment (large amplitude tip/tilt aberrations correction) and phasing (piston and small amplitude tip/tilt aberrations correction) modes. We derive a new algorithm for the alignment of the subapertures : ELASTICS. We quantify the novel algorithm performance by numerical simulations. We show that the residues are within the capture range of the fine algorithms. We also study the performance of LAPD, a recent real-time algorithm for the phasing of the sub-apertures. The closed-loop alignement of a 6 sub-aperture mirror provides experimental demonstration for both algorithms.L'alignement des sous-pupilles est une défi majeur pour les futurs télescopes segmentés ou réseaux de télescopes. Nous montrons ici qu'un analyseur de surface d'onde en plan focal n'utilisant que deux images peut corriger un système multi-pupille de manière complète et efficace, aussi bien pour l'alignement initial (correction des basculements de grande amplitude) que le cophasage (correction des perturbations de piston et basculement de petite amplitude). Nous établissons un nouvel algorithme (ELASTICS) pour l'alignement des sous-pupilles, dont nous quantifions les performances par simulation numérique et montrons que les résidus sont inclus dans la zone d'accrochage des algorithmes fins. Nous étudions aussi les performances de LAPD, a algorithme temps-réel récent pour le cophasage des sous-pupilles. Une validation expérimentale de ces deux algorithmes a été effectuée par l'alignement en boucle fermée d'un miroir à 6 sous-pupilles

Higher adaptive optics loop rate enhances axial resolution in nonconfocal ophthalmoscopes

International audienceIn this Letter, we propose a way to better understand the impact of dynamic ocular aberrations in the axial resolution of nonconfocal adaptive optics (AO) ophthalmoscopes via a simulation of the 3D PSF in the retina for various AO-loop rates. We then use optical incoherence tomography, a method enabling the generation of tomographic retinal cross sections in incoherent imaging systems, to evaluate the benefits of a fast AO-loop rate on axial resolution and, consequently, on AO-corrected retinal image quality. We used the PARIS AO flood-illumination ophthalmoscope for this study, where retinal images from different focal planes at an AO-loop rate of 10 and 50 Hz were acquired

Optical design of a Michelson wide-field multiple-aperture telescope

Communication to : Optical system design, Saint Etienne (France), 29 Septembre - 3 Octobre 2003SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2004 n.205 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

DARWIN fringe sensor (DWARF) : concept study

Communication to : Towards other earths, Heidelberg (Hollande), 22-25 avril 2003Available from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2004 n.206 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Cophasing a wide field multi-aperture array by phase diversity : influence of aperture redundancy and dilution

Communication to : SPIE astronomical telescopes and instrumentation, Hawaii (USA), August 22-28, 2002SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2003 n.29 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Invasive aspergillosis due to Aspergillus cryptic species: A prospective multicentre study

International audienceObjectivesAspergillus cryptic species are increasingly recognised causes of Aspergillus diseases, including life-threatening invasive aspergillosis (IA). However, as their accurate identification remains challenging in a routine practice, few is known from a clinical and epidemiological perspective. Recently, the MSI application has emerged as a powerful tool for the detection and identification of Aspergillus cryptic species. We aimed to use to the network of users of the MSI application to conduct a multicentre prospective screening of Aspergillus cryptic species-related IA and analyse their epidemiological, clinical and mycological characteristics.MethodsOver a 27-month period, the clinical involvement of 369 Aspergillus cryptic isolates, from 13 French and Danish MSI application users, was prospectively analysed. Species identification was confirmed by DNA-sequencing and antifungal susceptibility testing was performed using EUCAST reference method. Fifty-one A fumigatus sensu stricto invasive cases were also analysed.ResultsFifteen cryptic isolates were responsible of IA. Eight species were involved, including 5 cases related to the species A sublatus. These species showed high rate of in vitro low susceptibility to antifungal drugs. In comparison with A fumigatus sensu stricto invasive cases, pre-exposure to azole drugs was significantly associated with cryptic IA (P = .02).DiscussionThis study brings new insights in cryptic species related IA and underlines the importance to identify accurately at the species level these Aspergillus isolates. The increasing use of antifungal drugs might lead in the future to an epidemiologic shift with an emergence of resistant isolates involved in IA

SPICA, a new 6T visible beam combiner for CHARA: science, design and interfaces

International audienc